The present invention relates to a measuring method and systems for the determination of concentrations or velocities of flows or currents. It more particularly relates to a measuring method and a system to apply the measuring method according to the definition of the claims.
The determination of concentrations or velocities of flows or currents is of great importance in research and industry. It is e.g. about multiphase flows of solids in gases or liquids, or gas bubbles in liquids, or of liquid droplets in gases or liquids etc. It is also e.g. about moving matter, bulk solids, liquids, surfaces of liquids, webs of paper and fabric etc. The determination of concentrations or velocities of flows or currents reveals a variety of information as e.g. densities, degree of turbulence etc.
Existing measuring methods as e.g. the dust concentration measurement according to the transmission principle or e.g. the laser Doppler anemometry have disadvantages. These measuring systems are susceptible to soiling and may not be used at high or low temperatures, respectively. Therefore cleanings and dismantlements of the measuring systems are necessary, therefore continuos measurements/process monitoring becomes impossible. Such measuring systems are furthermore expensive and maintenance and application are costly.
It is the objective of the present invention to provide a measuring method for the determination of concentrations or velocities of flows or currents, which overcomes disadvantages of existing methods. It is a further objective of the invention to provide a measuring system, that eliminates disadvantages of existing systems. The measuring method and its measuring system should be compatible with existing and popular industry standards.
This objective is achieved by the invention according to the claims.
The invention serves to determine concentrations or velocities of flows or currents. It concerns flows consisting of different phases as e.g. solids in gases or liquids, or gas bubbles in liquids, or liquid droplets in gases or liquids etc. and it concerns flows as e.g. moving matter, bulk solids, liquids, surfaces of liquids, webs of paper and fabric etc.
For the determination of concentrations of flows or currents, physical quantities characteristic for concentrations as e.g. backscattered, emitted or transmitted light, radiation or sonic intensities, permeabilities, dielectric constants (permittivities), conductivities, diffractions of micro waves, magnetic or nuclear magnetic resonances (NMR) or temperatures are measured. For the quantitative determination of e.g. solids concentrations calibration parameters are determined by performing e.g. calibration experiments measuring characteristic physical quantities at different known concentrations and hence deriving a mathematical function. Such calibration parameters depend generally on the relevant physical properties of the materials of the flows or currents considered.
For the determination of velocities of flows or currents, the fluctuations of characteristic physical quantities as e.g. backscattered, emitted or transmitted light, radiation or sonic intensity, permeability, dielectric constant (permittivity), conductivity, diffraction of micro waves, magnetic or nuclear magnetic resonance (NMR) or temperatures, or are measured locally by means of two or three sensor heads and correlated using stochastic methods. The comparison of several of such measured measuring signals allows the correlative determination velocities of e.g. solids, clusters or bubbles. The velocity determination is performed for one or two dimensional flows or currents. The thus used measuring system comprises a measuring probe, in which all optical and electronical components are integrated and protected effectively from environmental influences. It further comprises a power supply for the supply of the measuring probe and a computerized analysis unit for the analysis of the measuring signals measured by the measuring probe. Particularly for the velocity determination, a measuring system with two or three sensor heads placed at different positions is used. The measuring resolution is determined by the distance of the sensor heads from each other. From correlations times of flight between the sensor heads are determined. Flow or current velocities result from quotients of distances of sensor heads and times of flight.